The term “carrier” is here to be construed as a material including at least one of the substances: granulated expanded vermiculite, perlite, zeolite, cellulose materials, such as wood fibres and sphagnum, burned clay, rock wool or the like substances, whereby it is possible to obtain a desired degree of water conveying capacity, ion exchanging properties etc.
The term “additive” is here primarily to be construed as water-absorbing materials, such as superabsorbing materials, i.e. absorption of H2O in order to achieve a moisture buffer, such as for instance superabsorbing polymers (SAP).
The expression “adjuvant” should here be understood so as to cover one or more substances selected among plant nutrients, plant protectants, such as pesticides, including herbicides, insecticides, especially systemic insecticides, fungicides, virae, cultures of bacteria, cultures of fungi, such as Trikoderma, fungus spores, microencapsulated fungicides, eggs from useful insects, such as predatory nematodes, fertilizers, enzymes, animal repellents, hormones, pH-adjusting agents, activated carbon, clay particles, trace elements, such as molybdenum, wood fibres or wood powder, kieselguhr, surfactants or other substances with a favourable effect on the germination and the growth of plants, where several substances are available in microencapsulated form.
The expression “biodegradable” material is here to be construed as a material gradually disintegrating and/or being part of the ordinary biological food chain within a measurable period when left alone in its natural state.
The handling of seed tapes is often encumbered with the problem that the carrier, the additives and the possible adjuvants have a tendency to sift out of the individual germinating units, viz. the pockets, which presents a rather disadvantageous feature because a careful control of the pesticides inserted, such as for instance Gaucho, is actually desired. In addition, extra care should be taken that the materials being inserted in the germinating units remain in the initial locations because the manufacturing of such seed tapes must be carried out at a very high speed, viz. several hundred m/min.
WO 00/00007A relates to a seed tape including successively arranged germinating units, and which further includes at least one carrier strip as well as at least one auxiliary layer of biodegradable, flexible, non-woven or film-like material arranged on said carrier strip; each germinating unit includes a mixture of granulated carrier, at least one granulated additive in addition to one or more seeds, said mixture plus the seeds being kept together to form at least one core portion in the germinating unit; the core portion made of said mixture includes locally adhered fibres of one or more thermoplastic materials which form a coherent, open network for keeping the granules of the mixture together. As the seed tape is moved with high speed it would be advantageous if a more reliable retention of the carrier, additives and the possible adjuvants in each germinating unit could be obtained.
U.S. Pat. No. 5,372,885 relates to a method of making bicomponent fibres. The document describes high performance bicomponent fibres made out of thermoplastic materials. By using these fibres as binder fibres the efficiency of the binding in the mixture would be certainly improved but not enough.